In response to the extreme drought that gripped Texas this year — and in the midst of raging wildfires — Governor Rick Perry declared Friday, April 22, to Sunday, April 24, as “Days of Prayer for Rain in the State of Texas.” Receiving no immediate rain in answer, he reaffirmed his efforts by calling to a nationwide array of churches to join him in prayer to end the drought. Nearly 30,000 people, many from outside of Texas, joined him in a seven-hour marathon in Reliant Stadium on Saturday, August 6.
It was not until October 6 — two months later to the day — that the plea for rain was answered. On that day, a cloudy morning broke into a heavy rain in Houston as well as other parts of Texas. Before the day was ended, Houston was blessed with copious precipitation as 3.02 inches of rain was recorded at the George Bush Intercontinental Airport. Somewhere immediately after October 20, Houston was, and remains, visited by a plague of mosquitoes of biblical proportion. Where did they come from and when will they leave?
Of these four events, the invasion of the mosquitoes is related to at least one of the three others in a causal fashion. Mosquitoes, in order to breed, must have a source of stagnant water. The rains of October 6 supplied that in a grand fashion. Water formed in discarded trash, depressions in the soil, grass-choked ditches and, most abundantly, puddles left in the storm sewers as the waters flowed to the Bayous and finally the Gulf of Mexico.
A female mosquito cannot lay her eggs until she finds stagnant water. There, she deposits somewhere around 300 eggs at a time. Imagine all of the mosquitoes of Houston just waiting around for still water and then laying their eggs almost in synchrony. Eggs hatch into larvae. Larvae develop through several instars and are transformed into pupae. Finally, the metamorphosis of the mosquito into an adult is completed within the pupal case. All of these stages in the life cycle of the mosquito take place on the surface of the water. The length of the egg, larvae and pupae stages all depends on the species of mosquito and the temperature.
A typical Houston mosquito staging at 80 degrees Fahrenheit takes about 10 to 14 days from the time it is laid to the time the fully adult mosquito leaves the surface of the water and flies into the night sky. If the watery breeding pond had collected on October 6 or so, the mosquito invasion should take place on or around October 20 — which is exactly what happened.
Now one cannot always predict what one will get when one asks for something — and I don’t think that Governor Perry had a mosquito invasion in mind when he asked for rain.
However, nature is a complicated system and is not always predictable by simple mortals. But I do think she regularly tries to send us lessons. Maybe she is most powerful and certainly unpredictable. But the rain was a good thing and every living thing in Houston, the trees, flowers, grass, dogs, etc., all grew and prospered as a result of the rain. So did the mosquitoes. We just need to wait for the next cold front to get relief.
Ronald L. Sass, Ph.D., is the fellow in global climate change at the Baker Institute and the Harry C. and Olga K. Wiess Professor Emeritus of Natural Sciences at Rice University. Now retired, he joined the Rice faculty in 1958 and served as chairman of the Ecology and Evolutionary Biology Department.